“Pantoprazole” is the international non-proprietary name of a substituted benzimidazole (5-(difluoromethoxy)-2-[[(3,4-dimethoxy-2-pyridinyl)methyl]sulfinyl]-1H-benzimidazole). It is a compound that inhibits gastric acid secretion. Pantoprazole sodium is a proton pump inhibitor (PPI) used to treat ulcers, gastroesophageal reflux disorder (GERD), erosive esophagitis and Zollinger-Ellison syndrome. It works by blocking acid production in the stomach. It may be used in combination with antibiotics (e.g., amoxicillin, clarithromycin) to treat certain types of ulcers.
The complete pharmacological and therapeutic effect for pantoprazole can be achieved in the acid secreting parietal cells. By means of a feed back mechanism, this effect is diminished at the same rate as acid secretion is inhibited. As with other proton pump inhibitors and H2 Receptor inhibitors, treatment with pantoprazole causes reduced acidity in the stomach causing a reversible increase in gastrin in proportion to the reduction in acidity. Pantoprazole sodium can be represented by the following structural formula.

Pantoprazole was disclosed for the first time in European patent application EP0166287.
In one of the processes described in this patent application, 2-chloromethyl-3,4-dimethoxy pyridine was reacted with 2-mercapto-5-difluoromethoxy benzimidazole to prepare a precursor sulfide, which was isolated and oxidized by using metachloroperbenzoic acid to yield pantoprazole base in a yield of 102% by weight with respect to 2-chloromethyl-3,4 dimethoxy pyridine.
PCT Application WO 97/29103 discloses the preparation of pantoprazole by coupling carbonyl fragments to form the sulfoxide precursor, which was further cyclised to obtain pantoprazole base.
PCT Application WO 02/28852 discloses synthesis of pantoprazole and the preparation of key intermediates useful in its synthesis. Pantoprazole base was prepared by oxidation of the chloro derivative of pantoprazole using ammonium per molybdate or ammonium per tungstate in the presence of hydrogen peroxide. Further the chloro group in the resulting product was replaced by methoxy group to obtain pantoprazole base, the yield being about 70% by weight of the pyridine precursor.
PCT Application WO 02/062786 discloses a process for preparation of pantoprazole base by oxidizing the precursor of pantoprazole (i.e. sulfide) using tertiary butyl hydroperoxide and oxone in yield of about 79% weight percent of the sulfide intermediate.
WO 91/19710 discloses pantoprazole sodium sesquihydrate and their typical characteristics.
U.S. Patent 04/0186139A1 describes the preparation of Crystalline Form-I of pantoprazole sodium sesquihydrate from pantoprazole free base by precipitation using various solvents.
It is evident from the teachings of the prior art that multiple steps are required for the synthesis of pantoprazole sodium. Also the intermediates involved for the synthesis need to be isolated at various steps, and further purification is required to get the desired purity of the final product. The use of multiple steps in the prior art results in a lower yield of pantoprazole sodium.
The prior art methods described above also involves the use of many hazardous reagents like hydrogen peroxide, metachloroperbenzoic acid, etc. Thus the processes from the prior art are unable to provide an environmentally safe and industrially applicable process with substantial yields.